exactly! I always have preached underdrive pulley's no longer are worth it. The A/C and alternator are already disengaged under large throttle which means the only thing that is underdriven is power-steering and engine cooling. The two things I would never want to have heat up more than normal.

I am pretty sure M3s in the EU and in other locales got this under the "Efficient Dynamics" feature. At the same time I am pretty sure US cars did not get this (perhaps early US M3s did not and later ones did).

Quote:

Originally Posted by W Cole

The chart above is definitely incorrect in regards to the macht schnell pulleys. I just installed them this past week and the crank pulley is smaller on both the power steering and alternator sides therefore the A/C has to be underdriven. The power steering pump pulley is definitely a different size than OEM so the power steering is being underdriven by a different amount than the A/C, but none the less both are underdriven.

Good catch. Extracting the required information to complete this small project seems to be next to impossible.

I am pretty sure M3s in the EU and in other locales got this under the "Efficient Dynamics" feature. At the same time I am pretty sure US cars did not get this (perhaps early US M3s did not and later ones did).

Good catch. Extracting the required information to complete this small project seems to be next to impossible.

All years of the US m3's had "brake regeneration " thing with the alternator disconnecting during acceleration. All A/C systems in bmw's and most late model cars have an A/C clutch that disengages under heavy throttle.

So with a pulley the a/c gets underdrive when cruising and at wot it does not matter as its not engaged. Then when off the pedal the altnerator you really do not want to get underdrive as that is when its charging.

Not saying there is not power to be had but it is from underdriving 2 things only-power steering and engine coolant-just not the 2 things I really want to have underdrive personally, especially living in high heat of the desert.

My point is cars awhile back gained much more from a pulley as parasitic losses were much more significant when you had the a/c engaged during WOT, alternator running at all times and heavier components.

If the m3 didn't have the water pump and went electric, it essentially would only be driving the power steering which we all know is going electric.

We are not far off from having maybe 1 or 2 things drive by a belt, or perhaps nothing at all in a few years with things going electric.

This is how the m3 should have gone about increasing performance and mileage in the f30. Take the s65, direct inject it and up the CR to boot. Upgrade to latest vanos tech and then worked on getting rid of the lat parasitic losses with an electric water pump, electric steering etc. Could have been an easy 450 hp reworked, way more efficient, and with a lighter body would have been a perfect car

All years of the US m3's had "brake regeneration " thing with the alternator disconnecting during acceleration. All A/C systems in bmw's and most late model cars have an A/C clutch that disengages under heavy throttle.

So with a pulley the a/c gets underdrive when cruising and at wot it does not matter as its not engaged. Then when off the pedal the altnerator you really do not want to get underdrive as that is when its charging.

Not saying there is not power to be had but it is from underdriving 2 things only-power steering and engine coolant-just not the 2 things I really want to have underdrive personally, especially living in high heat of the desert.

My point is cars awhile back gained much more from a pulley as parasitic losses were much more significant when you had the a/c engaged during WOT, alternator running at all times and heavier components.

If the m3 didn't have the water pump and went electric, it essentially would only be driving the power steering which we all know is going electric.

We are not far off from having maybe 1 or 2 things drive by a belt, or perhaps nothing at all in a few years with things going electric.

This is how the m3 should have gone about increasing performance and mileage in the f30. Take the s65, direct inject it and up the CR to boot. Upgrade to latest vanos tech and then worked on getting rid of the lat parasitic losses with an electric water pump, electric steering etc. Could have been an easy 450 hp reworked, way more efficient, and with a lighter body would have been a perfect car

Why do all of the pulleys replace the crank pulley then? We should have replacement water pump and power steering pulleys to only under drive these systems.

All years of the US m3's had "brake regeneration " thing with the alternator disconnecting during acceleration. All A/C systems in bmw's and most late model cars have an A/C clutch that disengages under heavy throttle.

Here are a few discussions on this topic (there are more).

Link 1.
Here is another link.One more with almost direct evidence.Here is a source also claiming no BER in the US.

In short, after reviewing all of the posts here and on other sites I would say that all NA model years of the M3 having BOTH features (AC and Alternator disengaging at high or WOT) is very debatable. It would be great to put this one to bed.

At the M-school, the instructors were very clear that it would be ok running A/C on the M3s (not allowed to run w/ windows down), as > 80% of WOT results in AC disengaging, which they asserted really wouldn't affect lap times in the competitive timing.

Quote:

Originally Posted by swamp2

Here are a few discussions on this topic (there are more).

Link 1.
Here is another link.One more with almost direct evidence.Here is a source also claiming no BER in the US.

In short, after reviewing all of the posts here and on other sites I would say that all NA model years of the M3 having BOTH features (AC and Alternator disengaging at high or WOT) is very debatable. It would be great to put this one to bed.

To my surprise, the tracks on the pulley for the two belts are of significantly different diameters. The track for the power steering and A/C belt is smaller the the one for the alternator and water pump belt.

I have the "early" kit with the single sided belt, I don't know if it has anything to do with it.

The first chance I have, I will bring it to work to get it measured. I will post back the results.

To my surprise, the tracks on the pulley for the two belts are of significantly different diameters. The track for the power steering and A/C belt is smaller the the one for the alternator and water pump belt.

I have the "early" kit with the single sided belt, I don't know if it has anything to do with it.

The first chance I have, I will bring it to work to get it measured. I will post back the results.

Have fun getting the A/C belt on lol. Mine is post 2009 so not sure if yours is different but the belt is short and it totally sucks getting it on. Feel free to PM me if you run into issues.

Since you have the later pulley, do the two tracks have different diameters on your pulley?

I curious to find out if it is a Dinan pulley characteristic only if it only applies to the earlier belt arrangement...

I am pretty sure the tracks are different but I honestly don't remember. It think it is because the belts are different. Are there numbers on your belts? I meant to write them down before install in case I needed to replace one but I forgot to like a moron. It's probably a good idea.